﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace SubstringForStringBuilder
{
    public static class SubstringForStringBuilder
    {
        public static StringBuilder Substring(this StringBuilder strB, int index, int length)
        {
            string str = strB.ToString();
            return new StringBuilder(str.Substring(index, length));
        }
    }
}
